6,493 research outputs found
The Impact of Radio AGN Bubble Composition on the Dynamics and Thermal Balance of the Intracluster Medium
Feeding and feedback of active galactic nuclei (AGN) are critical for
understanding the dynamics and thermodynamics of the intracluster medium (ICM)
within the cores of galaxy clusters. While radio bubbles inflated by AGN jets
could be dynamically supported by cosmic rays (CRs), the impact of CR-dominated
jets are not well understood. In this work, we perform three-dimensional
simulations of CR-jet feedback in an isolated cluster atmosphere; we find that
CR jets impact the multiphase gas differently than jets dominated by kinetic
energy. In particular, CR bubbles can more efficiently uplift the cluster gas
and cause an outward expansion of the hot ICM. Due to adiabatic cooling from
the expansion and less efficient heating from CR bubbles by direct mixing, the
ICM is more prone to local thermal instabilities, which will later enhance
chaotic cold accretion onto the AGN. The amount of cold gas formed during the
bubble formation and its late-time evolution sensitively depend on whether CR
transport processes are included or not. We also find that low-level, subsonic
driving of turbulence by AGN jets holds for both kinetic and CR jets;
nevertheless, the kinematics is consistent with the Hitomi measurements.
Finally, we carefully discuss the key observable signatures of each bubble
model, focusing on gamma-ray emission (and related comparison with Fermi), as
well as thermal Sunyaev-Zel'dovich constraints.Comment: accepted to Ap
Assembling thefacebook: Using heterogeneity to understand online social network assembly
Online social networks represent a popular and diverse class of social media
systems. Despite this variety, each of these systems undergoes a general
process of online social network assembly, which represents the complicated and
heterogeneous changes that transform newly born systems into mature platforms.
However, little is known about this process. For example, how much of a
network's assembly is driven by simple growth? How does a network's structure
change as it matures? How does network structure vary with adoption rates and
user heterogeneity, and do these properties play different roles at different
points in the assembly? We investigate these and other questions using a unique
dataset of online connections among the roughly one million users at the first
100 colleges admitted to Facebook, captured just 20 months after its launch. We
first show that different vintages and adoption rates across this population of
networks reveal temporal dynamics of the assembly process, and that assembly is
only loosely related to network growth. We then exploit natural experiments
embedded in this dataset and complementary data obtained via Internet
archaeology to show that different subnetworks matured at different rates
toward similar end states. These results shed light on the processes and
patterns of online social network assembly, and may facilitate more effective
design for online social systems.Comment: 13 pages, 11 figures, Proceedings of the 7th Annual ACM Web Science
Conference (WebSci), 201
A Bayesian Analogue of Gleason's Theorem
We introduce a novel notion of probability within quantum history theories
and give a Gleasonesque proof for these assignments. This involves introducing
a tentative novel axiom of probability. We also discuss how we are to interpret
these generalised probabilities as partially ordered notions of preference and
we introduce a tentative generalised notion of Shannon entropy. A Bayesian
approach to probability theory is adopted throughout, thus the axioms we use
will be minimal criteria of rationality rather than ad hoc mathematical axioms.Comment: 14 pages, v2: minor stylistic changes, v3: changes made in-line with
to-be-published versio
Investigation of quantitative measures related to reading disability in a large sample of sib-pairs from the UK
We describe a family-based sample of individuals with reading disability collected as part of a quantitative trait loci (QTL) mapping study. Eighty-nine nuclear families (135 independent sib-pairs) were identified through a single proband using a traditional discrepancy score of predicted/actual reading ability and a known family history. Eight correlated psychometric measures were administered to each sibling, including single word reading, spelling, similarities, matrices, spoonerisms, nonword and irregular word reading, and a pseudohomophone test. Summary statistics for each measure showed a reduced mean for the probands compared to the co-sibs, which in turn was lower than that of the population. This partial co-sib regression back to the mean indicates that the measures are influenced by familial factors and therefore, may be suitable for a mapping study. The variance of each of the measures remained largely unaffected, which is reassuring for the application of a QTL approach. Multivariate genetic analysis carried out to explore the relationship between the measures identified a common factor between the reading measures that accounted for 54% of the variance. Finally the familiality estimates (range 0.32–0.73) obtained for the reading measures including the common factor (0.68) supported their heritability. These findings demonstrate the viability of this sample for QTL mapping, and will assist in the interpretation of any subsequent linkage findings in an ongoing genome scan
Parental experience of interaction with healthcare professionals during their infant's stay in the neonatal intensive care unit.
OBJECTIVE: To explore the experiences of parents of infants admitted to the neonatal intensive care unit towards interaction with healthcare professionals during their infants critical care. DESIGN: Semi-structured interviews were conducted with parents of critically ill infants admitted to neonatal intensive care and prospectively enrolled in a study of communication in critical care decision making. Interviews were transcribed verbatim and uploaded into NVivo V.10 to manage and facilitate data analysis. Thematic analysis identified themes representing the data. RESULTS: Nineteen interviews conducted with 14 families identified 4 themes: (1) initial impact of admission affecting transition into the neonatal unit; (2) impact of consistency of care, care givers and information giving; (3) impact of communication in facilitating or hindering parental autonomy, trust, parental expectations and interactions; (4) parental perception of respect and humane touches on the neonatal unit. CONCLUSION: Factors including the context of infant admission, interprofessional consistency, humane touches of staff and the transition into the culture of the neonatal unit are important issues for parents. These issues warrant further investigation to facilitate individualised family needs, attachment between parents and their baby and the professional team
CFHT AO Imaging of the CLASS Gravitational Lens System B1359+154
We present adaptive optics imaging of the CLASS gravitational lens system
B1359+154 obtained with the Canada-France-Hawaii Telescope (CFHT) in the
infrared K band. The observations show at least three brightness peaks within
the ring of lensed images, which we identify as emission from multiple lensing
galaxies. The results confirm the suspected compound nature of the lens, as
deduced from preliminary mass modeling. The detection of several additional
nearby galaxies suggests that B1359+154 is lensed by the compact core of a
small galaxy group. We attempted to produce an updated lens model based on the
CFHT observations and new 5-GHz radio data obtained with the MERLIN array, but
there are too few constraints to construct a realistic model at this time. The
uncertainties inherent with modeling compound lenses make B1359+154 a
challenging target for Hubble constant determination through the measurement of
differential time delays. However, time delays will offer additional
constraints to help pin down the mass model. This lens system therefore
presents a unique opportunity to directly measure the mass distribution of a
galaxy group at intermediate redshift.Comment: 12 pages including 3 figures; ApJL accepte
Enhanced Zeeman splitting in Ga0.25In0.75As quantum point contacts
The strength of the Zeeman splitting induced by an applied magnetic field is
an important factor for the realization of spin-resolved transport in
mesoscopic devices. We measure the Zeeman splitting for a quantum point contact
etched into a Ga0.25In0.75As quantum well, with the field oriented parallel to
the transport direction. We observe an enhancement of the Lande g-factor from
|g*|=3.8 +/- 0.2 for the third subband to |g*|=5.8 +/- 0.6 for the first
subband, six times larger than in GaAs. We report subband spacings in excess of
10 meV, which facilitates quantum transport at higher temperatures.Comment: [Version 2] Revtex4, 11 pages, 3 figures, accepted for publication in
Applied Physics Letter
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